Prediction of suitable habitats for the Indo-Pacific humpback dolphin (Sousa chinensis) in the Beibu Gulf of China and Vietnam

Abstract

The Indo-Pacific humpback dolphin (Sousa chinensis) is a threatened coastal flagship species in Asian marine ecosystems, but the distribution of its suitable habitat remains unclear. In the present study, we characterized habitat relationships and predicted potential suitable habitats for humpback dolphins in the Beibu Gulf of China and Vietnam. Maximum entropy modeling identified six discontinuous areas in the Beibu Gulf, with a total area of 4396.8 km2, as suitable habitats for humpback dolphins. Of these, three suitable habitats covering 3948.7 km2 were known habitats, and three others covering an area of 448.1 km 2 at the border of China and Vietnam or in Vietnamese waters (Beilun River Estuary, Qinghua, and Rongshi) were newly identified. Exploratory line-transect surveys are strongly recommended to determine whether dolphins are present in these three areas. The predicted suitable habitat showed seasonal variation, which increased slightly in the dry season compared with that in the wet season. Bathymetry is the most important predictor for habitat suitability, in line with the known coastal distribution of humpback dolphins. Our research predicted specific suitable habitat distributions which can be used to develop practical protection measures, such as the establishment of marine protected areas for this species to monitor, mitigate, or prohibit harmful anthropogenic activities.